1. Field of the Invention
This invention relates generally to video processing and more particularly to a method and apparatus for pre-processing a video signal prior to encoding to improve a codec's efficiency while simultaneously reducing the effects of noise present in the video signal being encoded.
2. Description of the Related Art
Transmission of video data has become more popular as network bandwidth has increased to handle the bandwidth required for video data having an acceptable quality level. Video data requires a high bandwidth, i.e., many bytes of information per second. Therefore, video compression or video coding technology reduces the bandwidth requirements prior to transmission of the video data. However, the compression of the video data may negatively impact the image quality when the compressed video data is decompressed for presentation. For example, block based video compression schemes, such as Motion Picture Expert Group (MPEG) coding standard, suffer from blocking artifacts which become visible at the boundaries between blocks of a frame of the video image.
FIG. 1 is a simplified schematic diagram of a video coding system. Video capture device 100 captures image data. The image data is then compressed according to a compression standard through encoder 102. The compressed image data is then transmitted over network 104 to decoder 106. Decoder 106 may include post-processing block 108, which is configured to compensate for blocky artifacts. The decompressed image data that has been post processed is then presented on display monitor 110. Alternatively, placement of the processing block configured to compensate for blocky artifacts may be within encoder 102. Here, DCT domain filter 112 is included within encoder 102 to reduce blocky artifacts introduced during compression operations.
Thus, post-processing block 108 includes the capability to offset blocky artifacts, e.g., low pass filters applied to the spatial domain attempt to compensate for the artifacts introduced through the compression standard. However, one shortcoming with current post-processing steps is their computational complexity, which requires about 30-50% of the total computational power needed in the decoder, not to mention the dedication of compute cycles for post-processing functions. It should be appreciated that this type of power drain is unacceptably high for mobile terminals, i.e., battery enabled consumer electronics, such as terminals incorporating thin film transistors (TFT) technology, super-twisted nematic (STN), and mobile digital-thin film diode (MD-TFD). Another shortcoming of the low pass filters currently being used is that the amount of time for the filtering operation may cause a noticeable delay in the presentation of the image. This delay is especially noticeable with respect to portable electronic computing systems due to the limited resources of the embedded systems controlling these devices.
The current in-loop filtering represented through FIG. 1 is not capable of effectively handling noise introduced into the encoder loop from the input device in addition to smoothing blocky artifacts. Furthermore, since the noise from the input device tends to be random, the motion tracker of the encoder is fooled into following noise rather than the actual signal. For example, the motion tracker may take a signal at time t and then finds a location where the difference is close to 0. Thereafter, the motion tracker outputs a motion vector and the difference. However, random noise causes the difference to become the difference between the signal and the noise rather than the difference between the true motion. Thus, if the motion vector is dominant, then everything becomes influenced by noise rather than the actual signal.
As a result, there is a need to solve the problems of the prior art to provide a method and system for reducing input device generated noise from a video signal prior to the video signal being received by the encoder.